Des Moines, Iowa (CNN)The union representing federal government employees announced Thursday that it was backing Democratic front-runner Hillary Clinton for president, citing her work in protecting government jobs and standing up for collective bargaining rights.

The head of the American Federation of Government Employees said the union was confident they "can count on Hillary Clinton to help us" do their jobs, in a post on their website.

"Secretary Clinton shares AFGE's vision for a strong and vibrant government workforce that has the necessary tools and support needed to deliver vital programs and services to the American public," said J. David Cox, the union president.

Photos:Who have celebrities endorsed for the 2016 election?

Photos:Who have celebrities endorsed for the 2016 election?

Actor Scott Baio told Fox News host Jeanine Pirro that he's joined the Trump train because he likes Donald Trump's message and toughness. "It's very simple, because when he speaks I understand him," Baio explained. "He speaks like I speak. He communicates with people very well."

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Photos:Who have celebrities endorsed for the 2016 election?

Phil Robertson, best known for his role on the A&E reality television show "Duck Dynasty," has endorsed Texas Sen. Ted Cruz for the Republican nomination.

"Bernie's like a kush, like the best kind of weed you can get, because he's the answer to all our problems," Chong told CNN.

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Photos:Who have celebrities endorsed for the 2016 election?

Around 200 people crowded into a New Hampshire restaurant in January to see retired soccer star Abby Wambach (arms outstretched) and actress Lena Dunham (wearing the hat). Both endorsed Hillary Clinton.

"I'm embarrassed to say this, but it took me far too long to start voting," Dunham told the crowd. "I had been of legal age for more than four years before I cast my first vote in the 2008 presidential election. It's not that I didn't care, but I didn't believe that me caring mattered. It was impossible for me to comprehend that one young woman checking a box after waiting in a long line could matter on a national level."

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Clinton turned to a new celebrity surrogate -- singer Demi Lovato -- in an effort to win over young women in Iowa, a state where Sanders' strength depends largely on his ability to turn out the youth vote.

In January, Clinton and Lovato drew a crowd of largely young women to the University of Iowa campus, where Lovato vouched for Clinton. After performing her hit song "Confident," Lovato said: "I don't think there's a woman more confident than Hillary Clinton."

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UFC champion Ronda Rousey endorsed Sanders for president.

"I'm voting for Bernie Sanders, because he doesn't take any corporate money," Rousey told Maxim magazine. "I don't think politicians should be allowed to take money for their campaigns from outside interests."

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Actress Eva Longoria has been an outspoken Clinton supporter since Clinton's 2008 campaign.

She told TMZ in 2013 that if Clinton ran for President, she'd "absolutely" support her.

"Family Guy" creator Seth MacFarlane is a Sanders supporter. He introduced the Vermont senator at a rally in October, telling the crowd, "He's the only candidate on either side who truly seems to grasp the magnitude of the catastrophe (of climate change)."

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Basketball superstar Kareem Abdul-Jabbar wrote an op-ed in The Washington Post slamming GOP candidate Donald Trump and praising Sanders for how they've handled their campaigns.

He wrote that Sanders is "a mature, thoughtful and intelligent man."

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In an interview with The New York Times magazine, musician Kid Rock said that he was "very interested" in the things Republican presidential candidate Ben Carson has to say.

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Actor Chuck Norris has a very public bromance with former GOP candidate Mike Huckabee. When Huckabee announced his candidacy, Norris told The New York Times in a statement, "I still believe Mike Huckabee is the most qualified."

Norris also endorsed Huckabee when he ran for President in 2008.

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Actor James Woods took to Twitter to say how much he admired Republican presidential candidate Carly Fiorina, saying he was "proud to support this remarkable woman and her historic campaign." Fiorina suspended her candidacy in February.

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Television personality Kim Kardashian endorsed Clinton in a Facebook post shortly after the first GOP debate wrapped in August.

She took a selfie with Clinton, writing, "I got my selfie!!! I really loved hearing her speak & hearing her goals for our country! #HillaryForPresident."

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"Pawn Stars" star Rick Harrison told CNN's Chris Moody that he endorsed Republican presidential candidate Marco Rubio, but the decision could cost him. He said he was "deeply impressed" with Rubio when he first met him, but that as a celebrity, getting political does worry him "to a degree."

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Rapper 50 Cent announced his support for Clinton, telling The Daily Beast, "It's Hillary time!"

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AFGE represents 670,000 workers in the federal government, including those that work for the District of Columbia government.

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The endorsement -- which as first reported by The Associated Press - is the 18th national union endorsement for Clinton and will help the Democratic front-runner's campaign argue that she has solidified the national union movement around her candidacy, not that of Vermont Sen. Bernie Sanders.

Clinton accepted the endorsement in a statement on Thursday, pledging, as president, to "always stand up for workers' rights, fight to keep workers safe on the job, and protect retirement security, including defined benefit plans and Social Security."

The federal employee union came to its decision by sending questionnaires to all announced presidential candidates and conducted surveys of its membership. According to the union, "Clinton's support exceeded that of the next closest candidate's by a 2-1 margin."

The AFGE National Executive Council, the organizing body for the union, then voted this week to endorse Clinton.

Hillary Clinton accepts the Democratic Party's nomination for president at the Democratic National Convention in Philadelphia on July 28. The former first lady, U.S. senator and secretary of state was the first woman to lead the presidential ticket of a major political party.

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Before marrying Bill Clinton, she was Hillary Rodham. Here she attends Wellesley College in Massachusetts. Her commencement speech at Wellesley's graduation ceremony in 1969 attracted national attention. After graduating, she attended Yale Law School.

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Rodham was a lawyer on the House Judiciary Committee, whose work led to impeachment charges against President Richard Nixon in 1974.

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In 1975, Rodham married Bill Clinton, whom she met at Yale Law School. He became the governor of Arkansas in 1978. In 1980, the couple had a daughter, Chelsea.

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Arkansas' first lady, now using the name Hillary Rodham Clinton, wears her inaugural ball gown in 1985.

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The Clintons celebrate Bill's inauguration in Little Rock, Arkansas, in 1991. He was governor from 1983 to 1992, when he was elected President.

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Bill Clinton comforts his wife on the set of "60 Minutes" after a stage light broke loose from the ceiling and knocked her down in January 1992.

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In June 1992, Clinton uses a sewing machine designed to eliminate back and wrist strain. She had just given a speech at a convention of the International Ladies' Garment Workers Union.

Clinton accompanies her husband as he takes the oath of office in January 1993.

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The Clintons share a laugh on Capitol Hill in 1993.

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Clinton unveils the renovated Blue Room of the White House in 1995.

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Clinton waves to the media in January 1996 as she arrives for an appearance before a grand jury in Washington. The first lady was subpoenaed to testify as a witness in the investigation of the Whitewater land deal in Arkansas. The Clintons' business investment was investigated, but ultimately they were cleared of any wrongdoing.

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The Clintons hug as Bill is sworn in for a second term as President.

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The first lady holds up a Grammy Award, which she won for her audiobook "It Takes a Village" in 1997.

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The Clintons dance on a beach in the U.S. Virgin Islands in January 1998. Later that month, Bill Clinton was accused of having a sexual relationship with former White House intern Monica Lewinsky.

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Clinton looks on as her husband discusses the Monica Lewinsky scandal in the Roosevelt Room of the White House on January 26, 1998. Clinton declared, "I did not have sexual relations with that woman." In August of that year, Clinton testified before a grand jury and admitted to having "inappropriate intimate contact" with Lewinsky, but he said it did not constitute sexual relations because they had not had intercourse. He was impeached in December on charges of perjury and obstruction of justice.

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The first family walks with their dog, Buddy, as they leave the White House for a vacation in August 1998.

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President Clinton makes a statement at the White House in December 1998, thanking members of Congress who voted against his impeachment. The Senate trial ended with an acquittal in February 1999.

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Clinton announces in February 2000 that she will seek the U.S. Senate seat in New York. She was elected later that year.

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Clinton makes her first appearance on the Senate Environment and Natural Resources Committee.

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Sen. Clinton comforts Maren Sarkarat, a woman who lost her husband in the September 11 terrorist attacks, during a ground-zero memorial in October 2001.

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Clinton holds up her book "Living History" before a signing in Auburn Hills, Michigan, in 2003.

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Clinton and another presidential hopeful, U.S. Sen. Barack Obama, applaud at the start of a Democratic debate in 2007.

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Obama and Clinton talk on the plane on their way to a rally in Unity, New Hampshire, in June 2008. She had recently ended her presidential campaign and endorsed Obama.

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Obama is flanked by Clinton and Vice President-elect Joe Biden at a news conference in Chicago in December 2008. He had designated Clinton to be his secretary of state.

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Clinton, as secretary of state, greets Russian Prime Minister Vladimir Putin during a meeting just outside Moscow in March 2010.

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The Clintons pose on the day of Chelsea's wedding to Marc Mezvinsky in July 2010.

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In this photo provided by the White House, Obama, Clinton, Biden and other members of the national security team receive an update on the mission against Osama bin Laden in May 2011.

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Clinton checks her Blackberry inside a military plane after leaving Malta in October 2011. In 2015, The New York Times reported that Clinton exclusively used a personal email account during her time as secretary of state. The account, fed through its own server, raises security and preservation concerns. Clinton later said she used a private domain out of "convenience," but admits in retrospect "it would have been better" to use multiple emails.

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Clinton arrives for a group photo before a forum with the Gulf Cooperation Council in March 2012. The forum was held in Riyadh, Saudi Arabia.

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Obama and Clinton bow during the transfer-of-remains ceremony marking the return of four Americans, including U.S. Ambassador Christopher Stevens, who were killed in Benghazi, Libya, in September 2012.

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Clinton ducks after a woman threw a shoe at her while she was delivering remarks at a recycling trade conference in Las Vegas in 2014.

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Clinton, now running for President again, performs with Jimmy Fallon during a "Tonight Show" skit in September 2015.

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Clinton testifies about the Benghazi attack during a House committee meeting in October 2015. "I would imagine I have thought more about what happened than all of you put together," she said during the 11-hour hearing. "I have lost more sleep than all of you put together. I have been wracking my brain about what more could have been done or should have been done." Months earlier, Clinton had acknowledged a "systemic breakdown" as cited by an Accountability Review Board, and she said that her department was taking additional steps to increase security at U.S. diplomatic facilities.

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U.S. Sen. Bernie Sanders shares a lighthearted moment with Clinton during a Democratic presidential debate in October 2015. It came after Sanders gave his take on the Clinton email scandal. "The American people are sick and tired of hearing about the damn emails," Sanders said. "Enough of the emails. Let's talk about the real issues facing the United States of America."

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Clinton is reflected in a teleprompter during a campaign rally in Alexandria, Virginia, in October 2015.

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Clinton walks on her stage with her family after winning the New York primary in April.

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After Clinton became the Democratic Party's presumptive nominee, this photo was posted to her official Twitter account. "To every little girl who dreams big: Yes, you can be anything you want -- even president," Clinton said. "Tonight is for you."

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Obama hugs Clinton after he gave a speech at the Democratic National Convention in Philadelphia. The president said Clinton was ready to be commander in chief. "For four years, I had a front-row seat to her intelligence, her judgment and her discipline," he said, referring to her stint as his secretary of state.

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Clinton arrives at a 9/11 commemoration ceremony in New York on September 11. Clinton, who was diagnosed with pneumonia two days before, left early after feeling ill. A video appeared to show her stumble as Secret Service agents helped her into a van.

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Clinton addresses a campaign rally in Cleveland on November 6, two days before Election Day. She went on to lose Ohio -- and the election -- to her Republican opponent, Donald Trump.

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After conceding the presidency to Trump in a phone call earlier, Clinton addresses supporters and campaign workers in New York on Wednesday, November 9. Her defeat marked a stunning end to a campaign that appeared poised to make her the first woman elected US president.

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The endorsement is yet another union blow to Sanders, who has worked hard to court union support, including marching on multiple picket lines in an attempt to show his commitment to the effort. While that has yet to pay off for the independent senator, the Sanders campaign has routinely said after each national endorsement for Clinton that while union leadership is with Clinton, the people on the ground are with Sanders.

AFGE's endorsement is not binding for its local chapters and members. But in the post on its website, the union urged members to "close ranks and stand by her in what will no doubt be a long fight against a determined anti-government, anti-worker onslaught."